The present invention relates to one-dimensional scanners. More particularly, the invention relates to a one-dimensional scanner adapted to reduce the size of picture elements and accordingly increase the density of picture elements without decreasing the widths of the electrodes of conversion elements used to convert an optical image into an electrical signal or to convert a time-series electrical signal into an optical or thermal signal.
An example of an electro-optical conversion element in a conventional one-dimensional scanner is shown in FIGS. 1 and 2.
In FIG. 1, reference numeral 1 designates the electro-optical conversion element 1, 2 an upper transparent substrate, 3 an upper transparent electrode composed of a number of upper electrode elements arranged one-dimensionally in a scanning direction at a predetermined interval or pitch, 4 a lower transparent substrate, 5 a lower transparent electrode which is spaced from the upper transparent electrode 3 and provided in the form of a belt extending one-dimensionally in the scanning direction, 6 a liquid crystal layer provided between the upper and lower transparent electrodes 3 and 5, and 7 spacers.
FIG. 2 is an explanatory diagram showing the positional relationship between the upper and lower electrodes between which an electro-optical conversion material such as a liquid crystal layer is interposed.
In FIG. 2, reference characters 3-1, 3-2, . . . and 3-n designate the electrode elements of the upper transparent electrode, 5 the lower transparent electrode, and 8 picture cell regions which are formed between the upper transparent electrode 3 (i.e. the upper electrode elements 3-1, 3-2, . . . and 3-n) and the lower transparent electrode 5. When a voltage is applied across the upper and lower electrodes, the light-transmissivity of the liquid crystal layer therebetween is varied, thus controlling the incident light.
FIG. 3 illustrates the case where the electro-optical conversion element thus constructed is employed as a light valve one-dimensional scanner.
In FIG. 3, reference numeral 22 designates a photosensitive drum, 1a a light valve one-dimensional scanner disposed adjacent to the upper portion of the photo-sensitive drum 22, 21 the one-dimensional mask of the light valve one-dimensional scanner, and 20 a uniform, one-dimensional irradiation light beam.
First, the electro-optical conversion element 1 is irradiated one-dimensionally by the one-dimensional irradiation light beam 20 from above the upper transparent substrate 2. Then, in response to input signals, voltages are applied to the electrode elements one after another while the picture cell regions 8 are being scanned to thus vary the light-transmissivity of the liquid crystal layer 6 and thereby to control the amount of light which passes through the scanner.
In the employment of the above-described electro-optical conversion element, the density of the raster image (i.e. the picture element size) is defined by the pitch of the upper transparent electrode elements 3-1, 3-2, . . . and 3-n.
The electro-optical conversion element described above suffers from a drawback that, if it is desired to increase the image density (i.e. to increase the resolution by decreasing the picture element size), it is impossible to do so by decreasing the width and the pitch of the upper transparent electrode elements 3-1, 3-2, . . . and 3-n because decreasing the width and pitch is limited by manufacturing considerations. For instance, the minimum picture of the electrode elements of an electro-optical conversion elements which can be manufactured using practical processes for an original 300 mm in width is of the order of 50 .mu.m.
FIG. 4 is a sectional view of a conventional one-dimensional image reading element (RIS), i.e. a conventional photoelectric conversion element. In FIG. 4, reference numeral 19 designates the upper electrode, 17 the lower electrode composed of a number of lower electrode elements which are spaced from the upper electrode 19 and are arranged at a predetermined interval or pitch, 18 a photosensitive material layer provided between the upper and lower electrodes 19 and 17, and 16 the lower substrate.
Also in a one-dimensional image reading element in which, as shown in FIG. 4, the upper electrodes 19 or the lower electrode 17 is made transparent or at least one side (or the light incidence side) of the two sides of the lower substrate 16 is made transparent and a photosensitive material layer is interposed therebetween, and hence similar to the case of FIG. 1, the image density is defined by the pitch of the electrode elements. Thus, the one-dimensional image reading element is disadvantageous in that it is impossible to decrease the pitch of the electrode elements because of the structure and accordingly it is impossible to increase the image density.